NAB customers have been left without basic online banking services as the major bank suffers what appears to be a nationwide outage.

The outage follows a similar incident in October that forced the bank to apologise to its customers for the four-hour disruption to services.

Internet banking customers were presented with an error screen that read "NAB internet banking is unavailable" and recommended using the bank's mobile or telephone banking services.

However, after being redirected to mobile, customers were denied services further and presented with a screen that stated "Payments are temporarily unavailable within NAB Mobile Banking".

Customers took to Twitter to air their annoyance, and in a surprise move the bank has been responding to all queries as they appear.

Comments made by disgruntled customers on an outage website forum ranged from "annoying..." to "what a shit joke! no app or website... great job Nab